Internet Engineering Task Force (IETF) S. Litkowski
Request for Comments: 8333 B. Decraene
Category: Standards Track Orange
ISSN: 2070-1721 C. Filsfils
Cisco Systems
P. Francois
Individual Contributor
March 2018
Micro-loop Prevention by Introducing a Local Convergence Delay
Abstract
This document describes a mechanism for link-state routing protocols
that prevents local transient forwarding loops in case of link
failure. This mechanism proposes a two-step convergence by
introducing a delay between the convergence of the node adjacent to
the topology change and the network-wide convergence.
Because this mechanism delays the IGP convergence, it may only be
used for planned maintenance or when Fast Reroute (FRR) protects the
traffic during the time between the link failure and the IGP
convergence.
The mechanism is limited to the link-down event in order to keep the
mechanism simple.
Simulations using real network topologies have been performed and
show that local loops are a significant portion (>50%) of the total
forwarding loops.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8333.
Litkowski, et al. Standards Track [Page 1]RFC 8333 Micro-loop Prevention by Local Delay March 2018Copyright Notice
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Litkowski, et al. Standards Track [Page 2]RFC 8333 Micro-loop Prevention by Local Delay March 2018Table of Contents
1. Introduction ....................................................4
2. Terminology .....................................................4
2.1. Acronyms ...................................................4
2.2. Requirements Language ......................................5
3. Side Effects of Transient Forwarding Loops ......................5
3.1. FRR Inefficiency ...........................................5
3.2. Network Congestion .........................................8
4. Overview of the Solution ........................................9
5. Specification ...................................................9
5.1. Definitions ................................................9
5.2. Regular IGP Reaction ......................................10
5.3. Local Events ..............................................10
5.4. Local Delay for Link-Down Events ..........................11
6. Applicability ..................................................11
6.1. Applicable Case: Local Loops ..............................12
6.2. Non-applicable Case: Remote Loops .........................12
7. Simulations ....................................................13
8. Deployment Considerations ......................................14
9. Examples .......................................................15
9.1. Local Link-Down Event .....................................15
9.2. Local and Remote Event ....................................19
9.3. Aborting Local Delay ......................................21
10. Comparison with Other Solutions ...............................23
10.1. PLSN .....................................................23
10.2. oFIB .....................................................24
11. IANA Considerations ...........................................24